1. Technical Field
This invention relates to a beverage dispenser for storing drinking water from a raw water container in a tank and dispensing it through an extraction valve.
2. Background Art
In a beverage dispenser comprising a connecting portion on which a downwardly extending spout of a raw water container filled with drinking water is mounted, a tank provided below this connecting portion for storing the drinking water falling from the raw water container, and an extraction valve that extracts the drinking water stored in the tank, air comes into the tank from outside as the water level in the tank lowers. Many beverage dispensers of such kind have a cold tank with a cooling device and a hot tank with a heating device, being able to dispense cold water and hot water separately.
Thus in such a beverage dispenser, microbes such as bacteria and virus in the outside air are introduced into the tank with air, contaminating the drinking water inside the tank. In a beverage dispenser with a hard raw water container, in which air comes into the container as water in the container falls, drinking water in the raw water container is also contaminated by these bacteria. In a beverage dispenser with a soft raw water container, in which the container collapses as the water inside the container falls, air does not come into the container.
Known anti-bacterial means for such beverage dispensers include providing an ultraviolet bactericidal device immediately before the extraction valve (e.g. Patent Document 1); immersing an ultraviolet lamp in the tank and attaching an ultrasonic element to sterilize the water in the tank during agitation (e.g. Patent Document 2); providing a circulating path through which the drinking water extracted from the tank circulates and sterilizing with a means such as an ultraviolet lamp in the circulating path (e.g. Patent Document 3); for a dispenser with a cold tank and hot tank, providing a heat sterilizing device to sterilize water in the cold tank that is more prone to contamination (e.g. Patent Document 4); and to introduce heated drinking water from the hot tank to the cold tank, which is more prone to contamination (e.g. Patent Document 5).    Patent Document 1: JP 2000-85892A    Patent Document 2: JP U 3099926    Patent Document 3: JP 2005-350067A    Patent Document 4: JP 2004-315049A    Patent Document 5: JP 2005-170432A
All the anti-bacterial means for known beverage dispensers described in Patent Documents 1 to 5 kill bacteria after they are introduced into the drinking water from air. Therefore there may remain bacteria in the air in the tank or in the raw water container, and these bacteria may propagate. Large amounts of these propagated bacteria may be introduced into the drinking water and sterilizing is not done thoroughly.
Also, the means described in Patent Document 2 requires agitation means in the tank, and the means described in Patent Documents 3 and 5 requires the extra circulation path or an introduction path from hot tank to cold tank, which makes the beverage dispenser more complicated in structure and thus more costly. While the means in Patent Document 1 is simple in structure, its sterilizing may not be thorough enough. With the means in Patent Document 5, the cold water cannot be extracted during sterilizing in the cold tank.